Contents
- Weather in December
- Frequently asked questions
- Average temperature in December
- Average pressure in December
- Average wind speed in December
- Average humidity in December
- Average rainfall in December
- Average rainfall days in December
- Average snowfall in December
- Average snowfall days in December
- Average sea temperature in December
- Average daylight in December
- Average sunshine in December
- Average sunshine days in December
- Average UV index in December
- Average cloud cover in December
- Average visibility in December
Weather in December
Temperature
Start of December brings a slight shift in the average high-temperature, dipping a bit from November's fresh 51.8°F (11°C) to a frosty 43.7°F (6.5°C). A mean low-temperature of 36.5°F (2.5°C) is a distinguishing feature of December, indicating a slight dip from daytime highs.Humidity
The average relative humidity in December is 73%.Rainfall
The month with the most rainfall is December, when the rain falls for 11.4 days and typically aggregates up to 3.58" (91mm) of precipitation.Snowfall
January through March, October through December are months with snowfall. In Port Jefferson, in December, during 1.5 snowfall days, 1.06" (27mm) of snow is typically accumulated. Throughout the year, there are 12.6 snowfall days, and 5.59" (142mm) of snow is accumulated.Ocean temperature
In Port Jefferson, in December, the average water temperature is 48.9°F (9.4°C).Note: Taking a dip in 48.9°F (9.4°C) can be perilous. Submersion in temperatures under 50°F (10°C) triggers severe cold shock accompanied by hyperventilation.
Daylight
With an average of 9h and 18min of daylight, December has the shortest days of the year.On the first day of December in Port Jefferson, sunrise is at 6:58 am and sunset at 4:24 pm. On the last day of the month, sunrise is at 7:16 am and sunset at 4:34 pm EST.
Sunshine
The average sunshine in December is 4.8h.UV index
January through March, November and December, with an average maximum UV index of 2, are months with the lowest UV index. A UV Index value of 2, and less, symbolizes a low threat to health from exposure to the Sun's UV radiation for average individuals.Note: The UV index of 2 in December translates into these instructions:
Prolonged sun exposure should always be prevented in babies, children, and those with sensitive skin. Exposing oneself to the midday Sun can be harmful due to the strong UV radiation; limit your time outside. On days when the sun blazes, arm yourself with sunglasses that block UVA and UVB radiation. Remember to consider! The UV radiation from the Sun can be intensified nearly twice by the reflection of snow.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Is it cold during December?
What is the average humidity in December?
What is the wettest month?
How much does it rain in December?
How much does it snow in December?
How cold is the water in December?
What is the month with the shortest days?
What is the average length of the day in December?
What time are sunrise and sunset in December?
How many hours of sunshine does Port Jefferson have in December?
When is the lowest UV index?
What is the UV index intensity in December?
Average temperature in December
Port Jefferson, NY
- Average high temperature in December: 43.7°F
The warmest month (with the highest average high temperature) is July (79.2°F).
The month with the lowest average high temperature is January (37.6°F).
- Average low temperature in December: 36.5°F
The months with the highest average low temperature are July and August (71.1°F).
The coldest month (with the lowest average low temperature) is January (29.1°F).
Average pressure in December
Port Jefferson, NY
- Average pressure in December: 30.06"Hg
The month with the highest atmospheric pressure is November (30.09"Hg).
The month with the lowest atmospheric pressure is June (29.93"Hg).
Average wind speed in December
Port Jefferson, NY
- Average wind speed in December: 12.7mph
The windiest month (with the highest average wind speed) is January (12.9mph).
The calmest month (with the lowest average wind speed) is July (8.3mph).
Average humidity in December
Port Jefferson, NY
- Average humidity in December: 73%
The months with the highest relative humidity are May and June (77%).
The month with the lowest relative humidity is November (71%).
Average rainfall in December
Port Jefferson, NY
- Average rainfall in December: 3.58"
The wettest month (with the highest rainfall) is December (3.58").
The driest month (with the least rainfall) is January (2.05").
Average rainfall days in December
Port Jefferson, NY
- Average rainfall days in December: 11.4 days
The month with the highest number of rainy days is July (16.5 days).
The month with the least rainy days is January (6.8 days).
Average snowfall in December
Port Jefferson, NY
- Average snowfall in December: 1.06"
The month with the highest snowfall is March (2.13").
The months with the least snowfall are April, May, June, July, August and September (0").
Average snowfall days in December
Port Jefferson, NY
- Average snowfall days in December: 1.5 days
The month with the highest number of snowfall days is February (4.4 days).
The months with the least snowfall days are May, June, July, August and September (0 days).
Average sea temperature in December
Port Jefferson, NY
- Average sea temperature in December: 49°F
The best month for swimming (with the highest average sea temperature) is August (74°F).
The coldest month (with the lowest average sea temperature) is February (39.7°F).
Average daylight in December /
Average sunshine in December
Port Jefferson, NY
- Average daylight in December: 9h and 2min
The month with the longest days is June (Average daylight: 15h and 6min).
The month with the shortest days is December (Average daylight: 9h and 18min).
- Average sunshine in December: 4h and 5min
The month with the most sunshine is July (Average sunshine: 10h and 36min).
The month with the least sunshine is February (Average sunshine: 4h and 42min).
Average sunshine days in December
Port Jefferson, NY
- Average sunshine days in December: 17.6 days
The month with the most sunshine days is November (20.5 days).
The month with the least sunshine days is July (13 days).
Average UV index in December
Port Jefferson, NY
- Average UV index in December: 2
The months with the highest UV index are June, July and August (UV index 6).
The months with the lowest UV index are January, February, March, November and December (UV index 2).
Average cloud cover in December
Port Jefferson, NY
- Average cloud cover in December: 49
The month with the most cloud cover is December (Cloud cover 49).
The month with the least cloud cover is August (Cloud cover 28).
Average visibility in December
Port Jefferson, NY
- Average visibility in December: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
Port Jefferson, New York, USA
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